Humidity control devices have been conventionally known that use a hygroscopic liquid such as lithium chloride to control the humidity. Such a humidity control device has: a processor for performing a process of taking in air from a target space, dehumidifying or humidifying the taken-in air, and returning the air to the target space; and a regenerator for regenerating the hygroscopic liquid used by the processor.
A hygroscopic liquid of a high solution concentration absorbs moisture as the temperature decreases, and a hygroscopic liquid of a low solution concentration releases moisture as the temperature increases. Taking advantage of this nature, a humidity control device controls the humidity and regenerates a hygroscopic liquid by controlling the temperature of the hygroscopic liquid to be supplied to the processor and regenerator. Here regenerating a hygroscopic liquid means to restore the concentration of the hygroscopic liquid changed due to humidity control to the same condition as before the humidity control. For example, when dehumidification is performed, moisture in air is absorbed by a hygroscopic liquid by cooling the hygroscopic liquid of a high solution concentration and passing air through the cooled hygroscopic liquid. Since this process makes the hygroscopic liquid absorb moisture, the solution concentration of the hygroscopic liquid decreases. Sufficient dehumidification cannot be performed with the hygroscopic liquid of a low solution concentration, and thus the hygroscopic liquid is restored to the hygroscopic liquid of a high solution concentration by desorbing moisture from the hygroscopic liquid. On the other hand, when humidification is performed, the solution concentration of the hygroscopic liquid increases, and thus the hygroscopic liquid is restored to the hygroscopic liquid of a low solution concentration by making the hygroscopic liquid absorb moisture.
The present applicants have suggested a humidity control device that has improved energy utilization efficiency by means of a heat pump (Japanese Patent Laid-Open Application No. 2005-214595). The reason why energy utilization efficiency is improved by using a heat pump is as follows. In the humidity control device, the processor and the regenerator inversely control the temperature of the hygroscopic liquid. When a dehumidification operation is performed, the processor cools the hygroscopic liquid to perform dehumidification and the regenerator heats the hygroscopic liquid to remove moisture therefrom. When a humidification operation is performed, the processor heats the hygroscopic liquid to perform humidification and the regenerator cools the hygroscopic liquid to make it take in moisture. A heat pump is used to utilize heat absorbed from the cooling side (evaporator) for the heating side (condenser) without getting rid of the heat, and therefore energy utilization efficiency can be improved.
The humidity control device using a heat pump described in Japanese Patent Laid-Open Application No. 2005-214595 has a heat source on the regenerator side in addition to the heat pump. This is because if the humidity and regeneration are controlled only by the heat pump, the regeneration process on the regenerator side is restricted by the operating condition of the processor side, and the operation of the processor side sometimes cannot be balanced with that of the regenerator side. In order to prevent such inconvenience, the regenerator is provided with a heat source separate from the heat pump so that the regeneration process can be performed independently of the operating condition of the processor.